Fuel injection mechanism



Nov. 26, 1968 A. W. CAREY, JR.. ETAL FUEL INJECTION MECHANISM Filed Sept. 2, 1966 United States Patent Ofice 3,412,717 FUEL INJECTION MECHANISM Alfred W. Carey, Jr., and Julius P. Perr, Columbus, Ind.,

assignors to Cummins Engine Company, Inc., Columbus, Ind., a corporation of Indiana Filed Sept. 2, 1966, Ser. No. 577,045 7 Claims. (Cl. 12332) ABSTRACT OF THE DISCLOSURE A fuel injecting mechanism for injecting fuel into the cylinder of an internal combustion engine, including a fuel injector having a plunger reciprocably mounted therein, a cam for effecting cyclic movement of the plunger, linkage interconnecting the cam and injector plunger, and a spring engaging the injector plunger and causing the plunger to follow the movement of the cam. The mechanism also includes adjusting means for automatically decreasing the length of the linkage when the linkage is loaded due to the force of the spring and the reaction force caused by engagement of the plunger with the injector body at the completion of the injection stroke thereof. The adjusting means also automatically increases the length of the linkage to compensate for any decrease in length due to the force of the spring, or other causes, and is rendered operable to increase the length of the linkage when the linkage is unloaded upon engagement of the plunger with a stop on the injector.

This invention relates to fuel injection systems for internal combustion engines and more particularly to a fuel injector and mechanism for actuating the latter.

A general object of the invention is to provide a novel mechanism for injecting fuel into a cylinder of an internal combustion engine, which automatically prevents any clearance from developing between the parts of the mechanism during operation.

Another object is to provide a novel fuel injecting mechanism of the foregoing character, which eliminates the need for periodically adjusting the mechanism.

A further object is to provide a novel fuel injecting mechanism of the foregoing character, which is etiicient and reliable in operation, simple in construction, and inexpensive to manufacture.

Other objects :and advantages will become apparent from the following detailed description and accompanying drawing, in which:

FIG. 1 is a fragmentary sectional view through a portion of an internal combustion engine of the diesel type and showing a fuel injecting mechanism embodying the invention; and

FIG. 2 is a fragmentary view of a portion of the mechanism illustrated in FIG. 1 and showing a modified construction thereof.

Briefly described, the present invention is embodied in a novel mechanism for injecting fuel into a cylinder of a diesel engine, which automatically prevents any clearance from developing in the mechanism during operation of the engine. The mechanism, to be hereinafter described in detail, comprises a fuel injector having an elongated injector body adapted to be mounted in the cylinder head of the engine, and having a bore therein and at least one nozzle opening at one end of the bore. A plunger is reciprocably mounted in the bore for injecting fuel into the cylinder upon movement of the plunger in one direction toward the nozzle opening, the plunger moving into engagement with such end of the bore in order to completely inject the fuel into the cylinder. The injector also includes spring means tending to move the plunger in the opposite direction or away from the nozzle opening.

3,412,717 Patented Nov. 26, 1968 Cyclic movement of the plunger is controlled by engine driven means in the form of a cam, and linkage connecting the cam and plunger. Such linkage includes a pivotally mounted rocker arm and a pair of push' rods located :at the respective ends of the rocker arm, the push rods being respectively connected to the end of the plunger and to the cam. The mechanism is placed under load by the injector plunger spring and by engagement of the plunger with the injector body at the completion of the injection stroke of the plunger. For unloading the mechanism, stop means is provided on the injector for limiting movement of the plunger away from the nozzle opening, the position of such stop means on the injector being adjustable.

The mechanism also includes :adjusting means for automatically increasing the length of the linkage to compensate for any decrease in length due to wear or other causes. The adjusting means is in the form of a screw threaded into one end of the rocker arm and engaged by the associated push rod, a torsion spring being provided tending to rotate the screw in a direction to lengthen the linkage. Thus, when the plunger engages the stop means and the mechanism is unloaded, the screw is rotated by the spring in a direction to increase the length of the linkage and thereby prevent any clearance from developing in the mechanism.

In order to prevent the screw from becoming immobile and to maintain the screw free to rotate to perform its length increasing function, the screw is caused to rotate in a reverse direction to decrease the length of the linkage when the mechanism is under load and the plunger is moving. Consequently, when the plunger engages the stop means and the screw rotates in a direction to increase the length of the linkage, the screw will take up the previous ly induced decrease in the length of the linkage due to rotation of the screw in the reverse direction as well as any decrease in the length of the linkage due to wear or other causes.

In FIG. 1, a portion of the cylinder head, indicated at 11, and cylinder block, indicated at 12, of an internal combustion engine of the diesel type, are illustrated. The head 11 is provided with a bore 13 for receiving and retaining a fuel injector 14 for injecting fuel into an associated cylinder (not shown) of the engine in timed relation with the speed of the engine.

For illustrative purposes, the injector 14, in the present instance, is shown as comprising an elongated injector body including a body member 16 sized to fit the bore 13 in the cylinder head 11, and an injector cup 17 :at the lower end of the body member 16 and having at least one, and preferably a plurality of, nozzle openings 18 therethrough. A tubular retainer 19 is threaded onto the lower end of the body member 16 for securing the cup 17 thereto. The lower portion of the body member 16, cup 17 and retainer 19 are enclosed by a sleeve 20 having a tapered lower end 21 which is seated on a tapered seat 22 in the cylinder head 11 at the lower end of the bore 13.

The body member 16 has a central axial bore therethrough, in which a plunger 23 is reciprocably mounted. Such bore, in the present instance, includes a portion 24 in the body member 16 and another portion 25 provided by the interior of the cup 17, the portion 25 having its lower end tapered as at 26 and leading to the nozzle openings 18. The lower end, indicated at 27, of the plunger 23 is also tapered for engaging the tapered end 26 of the bore in the cup 17. When the lower end 27 of the plunger 23, during its reciprocation, is spaced from the tapered end 26 of the bore, a chamber is defined therebetween for receiving a quantity of fuel to be injected into the cylinder through the nozzle openings 18 upon movement of the plunger 23 toward the nozzle openings. The tapered end 26 of the bore in the cup 17 also serves to limit movement of the plunger 23 toward the nozzle openings 18. An injector of the foregoing character is disclosed in the copending Julius P. Perr application, Ser. No. 354,572, filed Mar. 25, 1964.

The injector plunger 23 is urged upwardly in its bore, as viewed in FIG. 1, or away from the nozzle openings 18 by a spring 32. In the present instance, the lower end of the spring 32 bears against a shoulder 33 defined by an annular, radially inwardly extending flange 34 at the lower end of a tubular extension 35 which encloses the spring, the extension 35 being seated on a shoulder 36 adjacent the upper end of the body member 16. A clamp (not shown), secured to the cylinder head 11, bears against an external shoulder 37 around the lower end of the extension 35 to hold the extension engaged with the body member 16 and the tapered lower end 21 of the injector sleeve engaged against its seat 22 in the cylinder head. In order to provide a seat for the upper end of the spring 32, a tubular spring retainer 38 having an annular radially outwardly extending flange 39 around its upper end, is secured to the upper end of the injector plunger 23, the upper end of the spring 32 engaging the flange 39.

Upward movement of the plunger 23 in its bore is limited by stop means in the form of an adjustable member 42 of inverted cup-shape having an end wall 43 and cylindrical side wall 44 threaded onto the upper end of the tubular extension 35. Thus, when the spring retainer flange 39 engages the end wall 43, further upward movement of the plunger 23 is prevented. Such limitation of upward movement of the plunger 23 assures greater accuracy in the fuel metering portion of the operating cycle of the injector 14. A look nut 48 may be provided on the extension to secure the adjustable member 42 in an adjusted position.

Movement of the injector plunger 23 in one direction toward the nozzle openings 18 to inject fuel into the cylinder is effected by engine driven means in form of a cam 46 and linkage interconnecting the cam 46 with the injector plunger 26. Such linkage, in the present instance, comprises a cam follower 52 mounted in a bore 53 in the engine block 12 and having a roller 54 engaging the cam 46, a push rod 55 extending between the follower 52 and one end 57 of a rocker arm 58, and another push rod or link 59 extending between the other end, indicated at 60, of the rocker arm 58 and the upper end, indicated at 61, of the injector plunger 23. The end wall 43 of the stop 42 is provided with an opening 49 to accommodate the link 59.

The rocker arm 58 is pivotally mounted intermediate its ends on a shaft (not shown) mounted on the cylinder head 11 of the engine and the other end 60 of the rocker arm is provided with an inverted cup-shaped depression 62 for receiving the complementally shaped upper end, indicated at 63, of the link '59. The lower end, indicated at 64, of the link 59 is rounded and seats in a hemispherically shaped recess in the upper end 161 of the injector plunger 23 and within the tubular extension 35. The link 59 includes a reduced diameter portion 66 slidably mounted in a guide sleeve 67 fixed in the upper end of the spring retainer 38.

The cam 46, which controls movement of the plunger 23, includes an outer base circle portion 69 for holding the tapered lower end 27 of the injector plunger 23 engaged with the lower end 26 of the plunger bore portion 25, and an inner base circle portion 70. The outer and inner base circle portions 69 and 70 of the cam 46 are connected by ramp portions 72 and 73. The cam 46 also includes another portion 71, the lift of which as shown in FIG. 1, is exaggerated. The portion 71 is located between the ramp portion 73 and the outer base circle portion 69 and forms a continuation of the ramp portion 73. The portion 71 displaces the plunger 23 beyond the position it occupies when the linkage is engaged by the outer base circle portion 69 of the cam, such further displacement of the plunger causing slight defQIlDfiIlQ!) of the cup 17.

With the foregoing construction, it will be apparent that, as the cam 46 rotates in a counterclockwise direction, as indicated by the arrow 74 in FIG. 1, the injector plunger 23 will be caused to reciprocate in its bore in accordance with the profile of the cam. Thus, assuming the roller 54 of the cam follower 52 is engaged with the outer base circle portion 69 of the cam 46, as shown in FIG. 1, the lower end 27 of the plunger will be held in engagement with the lower end 26 of the plunger bore as the cam 46 rotates. When the roller 54 begins to move down the ramp portion 72, the plunger 23 will begin to move upwardly in its bore, or away from the nozzle openings 18, due to the force of the spring 32 acting on the retainer 38. Such upward movement continues until the plunger 23 reaches its upper limit position when the flange 39 of the spring retainer 38 engages the end wall 43 of the adjustable member 42. Such engagement preferably occurs shortly before the roller 54 of the cam follower 52 moves onto the inner base circle 70.

Thus, the plunger 23 will be held in its upper limit position with the flange 39 of the spring retainer 38 engaged with the end wall 43 of the adjustable member 43 until the roller 54 moves onto the ramp portion 73 of the cam. At this time, the plunger 23 begins to move downwardly, or toward the lower end 26 of its bore to begin the fuel injection portion of its stroke. Downward movement of the plunger 23 continues as the roller 54 of the cam follower 52 advances along the ramp portion 73 until the lower end 27 of the plunger seats in the lower end 26 of its bore. When thus seated, fuel in the chamber in the lower end of the cup 17 will be injected into the cylinder through the nozzle openings 18 in the injector cup 17.

Complete discharge of all of the fuel in the chamber in the cup 17 is assured as the roller 54 of the cam fol lower 52 moves over the portion 71 (shown exaggerated in FIG. 1) of the cam, which causes a slight additional downward travel of the plunger 23 in its bore, causing slight deformation of the injector body. Movement of the roller 54 off of the portion 71 of the cam and onto the outer base circle portion 69 completes the cycle of movement of the plunger 23.

From the foregoing, it will be apparent that injection is ended sharply and reduced fuel economy and incomplete combustion resulting in a smoky exhaust are avoided, and an adequate seal is provided against combustion products such as carbon particles entering the fuel recirculation system of the injector, which might cause damage to other components of the fuel system. If clearance should develop in the mechanism due to wear or other causes, the sharp cut off would not be obtained and these difficulties would occur. To avoid this, novel adjusting means is provided to prevent any such clearance from occurring.

Such adjusting means, indicated generally at 75, is located in the linkage of the mechanism and comprises, in the present instance, a screw threaded into the end 57 of the rocker arm 58 for engaging the upper end of the push rod 55, and a torsion spring 82 engaging the screw and tending to rotate the latter in a direction to cause it to thread out of the rocker arm 58 to increase the length of the linkage. The threads, indicated at 86 and 87, of the screw 80 and rocker arm 58, respectively, are not required to be of particularly high pitch but are such that the screw 80 will thread into or out of the rocker arm 58 when a coefficient of dynamic friction between the threads is applicable. When a coefficient of static friction is applicable, the screw 80 will not turn because the coeflicient for static friction is much higher. A coefficient of dynamic friction occurs when there is angular variation between the axis of the screw 80 and the axis of the push rod 55, which results in a slight shifting of the screw 80 in the rocker arm 58. Such angular variation occurs during pivotal movement of the rocker arm 58 or when the roller 54 of the cam follower 52 engages the ramp portions 72 and 73 of the cam 46. Such shifting changes the coefficient of friction between the screw threads 86 and rocker arm threads 87 from that for static friction to that for dynamic friction, thereby substantially reducing the force required to rotate the screw 80. Consequently, the length of the linkage will decrease when the roller 54 of the cam follower 52 is engaged with the ramp portions 72 and 73 of the cam 46.

In order to accommodate relative angular movement between the upper end of the push rod 55 and the lower end, indicated at 88, of the screw 80, these parts preferably have the form of a ball and socket. Thus, the lower end 88 of the screw 80 is rounded and the upper end of the push rod 55 is formed with a hemispherical seat 92 for receiving the rounded lower end 88 of the screw 80. Lubrication of this joint is effected by a recess 94 in the push rod seat 92, which receives lubricant from connected passages 96 and 97 in the screw 80 and a bore 98 in the rocker arm 58 carrying lubricant under pressure. The bore 98 also serves to lubricate the screw threads 86 and rocker arm threads 87.

The spring 82 is preferably of the coil type and is arranged around the upper end of the screw 80 with an axially extending portion 102 at the lower end of the spring secured to the rocker arm 58 by being disposed in a bore 103 in the upper surface of the rocker arm. The upper end of the spring 82 engages the upper end of the screw 80 so as to exert a torsional force on the screw tending to rotate it in a direction to increase the length of the linkage. To this end, a portion 104 of the spring 82 is bent radially inward for extension into a transverse slot 106 in the upper end of the screw 80. The portion 104 is retained in the slot 106 by a hook 107 formed on the inner end of the portion 104, the hook 107 engaging a pin 108 mounted in the upper end of the screw and extending across the slot 106.

Prior to engagement of the portion 104 of the spring 82 in the slot 106, the screw 80 is rotated in a direction to take up any clearance in the mechanism and to impose a preload on the mechanism. Thereafter, the spring 82 is wound through an angle of approximately 125 degrees in a direction to exert the aforementioned torsional force on the screw and the portion 104 is inserted into the slot 106 of the screw 80 and the hook 107 engaged with the pin 108.

Unloading of the mechanism during a portion of the operating cycle of the injector 14 to permit the spring 82 to rotate the screw 80 in a direction to increase the length of the linkage and thus prevent any clearance from developing in the mechanism is achieved by the aforementioned stop means or adjustable member 42. Thus, when upward movement of the injector plunger 26 is arrested by the adjustable member 42, the force of the spring 32 is removed from the parts of the mechanism, thereby permitting the spring 82 to rotate the screw 80 in a direction to increase the length of the linkage and thus maintain contact between the parts of the mechanism.

The operation of the adjusting means 75 may be summarized as follows: Assuming that the roller 54 of the cam follower 52 is engaged with the outer base circle portion 69 of the cam 46 as illustrated in FIG. 1, the lower end 27 of the plunger 23 will be engaged with the tapered lower end 26 of the injector cup 17. The plunger will be held in such position throughout rotation of the cam 46 in the direction of the arrow 74 until the roller 54 of the follower 52 moves into engagement with the ramp portion 72 of the cam.

As the roller 54 moves down the ramp portion 72 toward the inner base circle portion 70, the rocker arm 58 will pivot on its shaft and thus change the angular relationship between the axes of the push rod 55 and screw 80 so that the latter is caused to shift in the rocker arm 58. Such shifting changes the coefficient of friction between the threads 86 and 87 of the screw and rocker arm from that for static friction to that for dynamic friction, as previously described, thereby permitting the screw to thread into the rocker arm 58 and decrease the length of the linkage. Such decrease continues as the roller 54 moves down the ramp portion 72 until the spring retainer 38 contacts the end wall 43 of the adjustable member 42. At this time, the force of the injector plunger spring 32 is relieved from the mechanism and from the screw threads 86 and rocker arm threads 87. Consequently, the torsion spring 82 of the adjusting means 75, which has been wound up an additional amount by the decrease in length of the linkage, becomes effective to rotate the screw 80 in a direction to thread the latter out of the rocker arm 58 and increase the length of the linkage to take up the previous decrease in length and toprevent any clearance from developing between the parts of the mechanism due to wear or other causes. Such increase in the length of the linkage terminates after the roller 54 moves onto the inner base circle 70 of the cam since the angle between the axis of the screw 80 and push rod 55 does not change when the roller 54 is engaged with the inner base circle portion 70 of the cam 46, and since any further increase would be opposed by the injector spring 32.

Continued rotation of the cam 46 brings the roller 54 of the follower 52 into engagement with the ramp portion 73, thereby causing upward movement of the push rod 55 and downward movement of the injector plunger 26 toward the lower end 26 of its bore. Since the screw 80 will have taken up the previous decrease in the length of the linkage and any decrease due to wear or other causes, the spring retainer flange 39 will immediately begin to move away from the end wall 43 of the adjustable member 42 when the roller 54 moves onto the ramp portion 73 of the cam. Consequently, the force of the injector spring 32 is again applied to the parts of the mechanism including the linkage and cam 46. The screw 80 will thus begin to thread into the rocker arm 58, as heretofore described, thereby decreasing the length of the linkage. Such decrease in length continues as the roller 54 advances along the ramp portion 73 of the cam including the portion 71. Movement of the roller 54 onto the outer base circle portion 47 of the cam completes the cycle of operation of the adjusting means 75.

From the foregoing it will be apparent that, during each cycle of movement of the plunger 23, the adjusting means 75 not only prevents any clearance from developing between the parts of the mechanism due to wear or other causes, but also compensates for any change in the length of the linkage due to dimensional changes in the parts of the engine and mechanism on changes in temperature. Moreover, rotation of the screw in opposite directions to decrease and increase the length of the linkage during each cycle of movement of the plunger 23 maintains the screw 80 of the adjusting means 75 free to rotate in the rocker arm 58. Consequently, the adjusting means 75 is maintained operable to perform its function throughout extended periods of operation of the engine, as heretofore described. The adjusting means 75 will continue to perform its function until the initial wind up or preload of the spring 82 has been exhausted which normally would not occur before 100,000 miles of engine operation.

In FIG. 2, an alternate construction of the stop means for limiting upward movement of the plunger (not shown) of a fuel injector 114, similar to the injector 14, is illustrated. Like reference numerals have been used to identify the parts of the mechanism illustrated in FIG. 2, which are identical with those of the mechanism of "FIG. 1. Thus, as shown in FIG. 2, the tubular spring extension, indicated at 122, which encloses the spring 32, is internally threaded as at 123 to receive an adjustable member in the form of an annular plug 124. The plug 124 may be provided with one or more circumferentially spaced bores 126 in the outer face thereof to receive a spanner wrench for rotating it.

7 When the plug member 124 is utilized, a collar 127 may be employed for confining the spring 32 and engaging the underside of the plug member 124. The collar 127 is urged into engagement with a flange 128 around the upper end of a tubular extension 129 having its lower end secured to the upper end of the plunger (not shown) of the injector 114. A push rod or link 131 extends between the other end 60 of the rocker arm 58 and the upper end of the plunger of the injector 114, the lower portion of the link 131 being enclosed by the tubular plunger extension 129.

We claim:

1. Mechanism for injecting fuel into a cylinder of an internal combustion engine, comprising a fuel injector including an elongated injector body having a bore therein and a nozzle opening at one end of said bore adapted to communicate with said cylinder, and a reciprocable plunger mounted in said bore for injecting fuel through said nozzle opening into said cylinder during movement of said plunger in one direction toward said nozzle opening, an engine driven cam for moving said plunger in saio one direction, linkage interconnecting said cam and said plunger, said plunger being limited in its movement in said one direction by engagement with said injector body at said one end of said bore, spring means tending to move said plunger in the opposite direction and thereby placing a load on said linkage, said load increasing when said plunger engages said one end of said bore, and stop means for limiting movement of said plunger in said opposite direction and thereby relieving said load on said linkage, said linkage including adjusting means for decreasing the length of said linkage during the period when said load is on said linkage and said plunger is moving and also when said plunger engages said injector body at said one end of said bore, said adjusting means also increasing the length of said linkage to automatically prevent clearance in the mechanism when said stop means relieves the load on said linkage.

2. The mechanism of claim 1, in which said injector includes an extension secured to the other end of said injector body, and said stop means includes an adjustable member mounted on said extension, said plunger including means for engaging said adjustable member on movement of said plunger in said opposite direction.

3. The mechanism of claim 2, in which said adjustable member is of inverted cup shape having its side wall threaded onto said extension.

4. The mechanism of claim 2, in which said adjustable member is in the form of an annular plug threaded into said extension.

5. The mechanism of claim 1, in which said cam has a ramp portion engageable by said linkage for moving said plunger in said one direction, an outer base circle portion engageable by said linkage for holding said plunger engaged with said injector body at said one end of said bore, and another portion engageable by said linkage and located between said ramp and outer base circle portions and forming a continuation of said ramp portion and for displacing said plunger beyond the position it occupies when said linkage is engaged with the outer base circle portion of said cam, said other portion of said cam imposing by deformation of said injector body an additional load on said linkage and thereby causing said adjusting means to further decrease the length of said linkage.

6. The mechanism of claim 5, in which said cam has another ramp portion engageable by said linkage and permitting movement of said plunger in said opposite direction, and an inner base circle portion engageable by said linkage and located between said ramp portions, both of said ramp portions and said other portion of said cam causing movement of said linkage and plunger to thereby render said adjusting means operable to decrease the length of said linkage.

7. The mechanism of claim 1, in which said linkage includes a rocker arm pivotally mounted intermediate its ends, and a pair of push rods located at the respective ends of said rocker arm and respectively connected to said plunger and to said cam, said adjusting means comprises a screw threaded into one end of said rocker arm and engaging the associated push rod, and a torsion spring engaging said rocker arm and said screw and tending to rotate said screw in a direction to increase the length of said linkage when said linkage is free of load, said screw rotating in a direction to decrease the length of said linkage during movement of said rocker arm when said linkage is under load from said spring means and when said plunger is in engagement with said one end of said bore, such rotation of the screw increasing the torsion of said spring, said torsion spring rotating said screw in a direction to increase the length of said linkage to automatically take up the decrease in length thereof occurring when said linkage is under load and also to take up wear occurring in the parts of the mechanism.

References Cited UNITED STATES PATENTS 2,418,110 4/ 1947 Burkhardt. 3,009,450 11/1961 Engemann. 3,034,488 5/ 1962 Reiners 123--32 3,110,293 11/1963 Reiners 123-32 LAURENCE M. GOODRIDGE, Primary Examiner. 

